Bilateral internuclear ophthalmoplegia with absence of convergent eye movements. Clinicopathologic correlation.

A case of bilateral internuclear ophthalmoplegia of long duration with autopsy confirmation is reported. The main features of the syndrome included paresis of ocular adduction upon attempted lateral gaze, horizontal nystagmus in the abducting eye, and an absence of converging eye movements. Examination of Weil-stained sections revealed multiple plaques of demyelination. The medial longitudinal fasciculus was demyelinated bilaterally in the upper pons-caudal midbrain. The oculomotor, trochlear, and abducens nuclei appeared relatively well preserved. The internal capsule was severely damaged. Large cyst-like structures were centered in the anterior limb bilaterally and extended caudally to the level of the genu. Plaques of demyelination were present bilaterally in the posterior limb. The left side of the internal capsule was more severely affected than the right. It is thought that convergence in this case may have been eliminated by interruption of fibers from the frontal eye fields and/or other cortical areas in their descent through the internal capsule.